1. Field of the Invention
The present invention relates to a clasp or releasable catch for holding together two complementary parts of a flexible article via interlocking engagement between a plug member and a socket member, and more particularly to such a releasable catch which can be coupled and uncoupled reliably with utmost ease and does not damage itself or another article in the coupled state.
2. Description of the Prior Art
Bags, such as rucksacks, briefcases and the like, of the type having a flap generally have a plug member attached to the flap, and a socket member attached to a body of the bag at an appropriate position where the plug member is to be locked in the socket member. When some stuff is to be put in or taken out from the bag, as a front side of the plug member is depressed, a locking tongue of the plug member is brought into and out of interlocking engagement with a gate-shaped locked portion of the socket member for closing and opening the flap.
The plug member includes an attachment portion attached to the flap and a locking tongue adapted to be locked in and released from the socket member. The locking tongue is provided with a resilient locking portion normally projecting from a front surface of the locking tongue. When the front side of the locking tongue is depressed, the locking portion retracts into the locking tongue. Conversely, when the pressure on the locking tongue is released, the locking portion resiliently projects again from the front surface of the locking tongue.
When the flap is to be caught on the body of the bag, the locking tongue of the plug member attached to the flap is forced into the gate-shaped locked portion of the socket member attached to the bag body. In this instance, the resilient locking portion of the locking tongue is depressed by the gate-shaped locked portion against the resiliency thereof and retracts into the locking tongue. A continued advancing movement of the locking tongue causes the resilient locking portion to move past the gate-shaped locked portion of the socket member whereupon the resilient locking portion springs back into its initial, projecting position and is thereby interlocked with the gate-shaped locked portion. On the other hand, when the flap is to be detached from the bag body, the plug member is pulled out to remove the locking tongue from the gate-shaped locked portion of the socket member while the resilient locking portion of the locking tongue is being manually depressed against the resiliency thereof. To achieve this uncoupling operation, the resilient locking portion must be retracted into the locking tongue while pulling the plug member away from the socket member. However, since most bag bodies are highly flexible, the bag body tends to become flexed or deformed when the socket member is depressed as a result of depression of the resilient locking portion of the plug member. Under such condition, an intended retracting movement of the resilient locking portion cannot take place with the result that a smooth coupling and uncoupling of the plug member and the socket member is almost difficult to achieve.
To facilitate a smooth uncoupling of the releasable catch, Japanese Utility Model Publication No. 57-47331 discloses a releasable catch including a socket member attached to the body of a bag. The socket has a base plate bent at its central portion into a stepped form which is composed of an upper locking portion and a lower attachment portion. The lower attachment portion is attached to the bag body so that the upper locking portion defines jointly with the bag body a space large enough to accommodate the user's finger. When a plug member attached to a flap of the bag is to be detached from the socket member on the bag body, the plug member is pulled while depressing a resilient locking portion of the plug member into a locking tongue of the plug member by gripping the plug member from the front and back sides with a finger received in the space between the upper locking portion of the socket and the bag body. The plug member thus gripped can readily be detached from the socket member. However, when the plug and socket members are in an assembled or coupled condition, the movement of the upper locking portion of the socket member is restrained. Accordingly, if the bag body is swelled or expanded by stuffs received in the bag, the space between the upper locking portion of the socket and the bag body is likely to disappear in which instance insertion of the user's finger behind the socket member is no longer possible.
To eliminate the foregoing defect, the present assignee proposed a bag which is equipped with a releasable catch so constructed as to insure easy coupling and uncoupling of a plug member and a socket member in all circumstances (see Japanese Utility Model Laid-open Publication No. 5-39322). The proposed bag is composed of a body to which is attached a plate-like socket member, and a flap to which is attached an attachment portion of a plug member. The plug member has a locking tongue resiliently deformable when depressed on its front side. The socket has on its front surface a gate-shaped locked portion with which the locking tongue of the plug member is releasably interlocked. The socket member has a lower end portion separated from the bag body and an upper end portion secured to the bag body.
However, in the bag disclosed in Japanese Utility Model Laid-open Publication No. 5-39322, the attachment portion and the lower end portion of the socket member lie substantially in the same plane and hence the socket member has a flat and straight plate-like configuration. Accordingly, when the bag body is swelled or expanded by stuffs received therein, the releasable catch tips up about the fixed upper end of the socket member so that the loose or unsecured lower end of the socket member sharply projects from the front surface of bag body. The thus projecting loose end of the socket member deteriorates the appearance of the bag and may be damaged in itself or damage another article when striking against the latter.